Rituparna Medda

Anti inflammatory and anti angiogenic effect of black raspberry extract on human esophageal and intestinal microvascular endothelial cells

Polyphenolic compounds (anthocyanins, flavonoid glycosides) in berries prevent the initiation, promotion, and progression of carcinogenesis in rats digestive tract and esophagus, in part, via anti-inflammatory pathways. Angiogenesis has been implicated in the pathogenesis of chronic inflammation and tumorigenesis. In this study, we investigated the anti-inflammatory and anti-angiogenic effects of black raspberry extract (BRE) on two organ specific primary human intestinal microvascular endothelial cells, (HIMEC) and human esophageal microvascular endothelial cells (HEMEC), isolated from surgically resected human intestinal and donor discarded esophagus, respectively. HEMEC and HIMEC were stimulated with TNF-α/IL-1β with or without BRE. The anti-inflammatory effects of BRE were assessed based upon COX-2, ICAM-1 and VCAM-1 gene and protein expression, PGE2 production, NFκB p65 subunit nuclear translocation as well as endothelial cell-leukocyte adhesion. The anti-angiogenic effects of BRE were assessed on cell migration, proliferation and tube formation following VEGF stimulation as well as on activation of Akt, MAPK and JNK signaling pathways. BRE inhibited TNF-α/IL-1β-induced NFκB p65 nuclear translocation, PGE2 production, up-regulation of COX-2, ICAM-1 and VCAM-1 gene and protein expression and leukocyte binding in HEMEC but not in HIMEC. BRE attenuated VEGF-induced cell migration, proliferation and tube formation in both HEMEC and HIMEC. The anti-angiogenic effect of BRE is mediated by inhibition of Akt, MAPK and JNK phosphorylations. BRE exerted differential anti-inflammatory effects between HEMEC and HIMEC following TNF-α/IL-1β activation whereas demonstrated similar anti-angiogenic effects following VEGF stimulation in both cell lines. These findings may provide more insight into the anti-tumorigenic capacities of BRE in human disease and cancer.

Endothelial-mesenchymal transition in normal human esophageal endothelial cells cocultured with esophageal adenocarcinoma cells: role of IL-1β and TGF-β2

Endothelial-mesenchymal transition (EndoMT) has been recognized as a key determinant of tumor microenvironment in cancer progression and metastasis. Endothelial cells undergoing EndoMT lose their endothelial markers, acquire the mesenchymal phenotype, and become more invasive with increased migratory abilities. Early stages of esophageal adenocarcinoma (EAC) are characterized by strong microvasculature whose impact in tumor progression remains undefined. Our aim was to determine the role of EndoMT in EAC by investigating the impact of tumor cells on normal primary human esophageal microvascular endothelial cells (HEMEC). HEMEC were either cocultured with OE33 adenocarcinoma cells or treated with IL-1β and transforming growth factor-β2 (TGF-β2) for indicated periods and analyzed for EndoMT-associated changes by real-time PCR, Western blotting, immunofluorescence staining, and functional assays. Additionally, human EAC tissues were investigated for detection of EndoMT-like cells. Our results demonstrate an increased expression of mesenchymal markers [fibroblast-specific protein 1 (FSP1), collagen1α2, vimentin, α-smooth muscle actin (α-SMA), and Snail], decreased expression of endothelial markers [CD31, von Willebrand factor VIII (vWF), and VE-cadherin], and elevated migration ability in HEMEC following coculture with OE33 cells. The EndoMT-related changes were inhibited by IL-1β and TGF-β2 gene silencing in OE33 cells. Recombinant IL-1β and TGF-β2 induced EndoMT in HEMEC. Although the level of VEGF expression was elevated in EndoMT cells, the angiogenic property of these cells was diminished. In vivo, by immunostaining EndoMT-like cells were detected at the invasive front of EAC. Our findings underscore a significant role for EndoMT in EAC and provide new insights into the mechanisms and significance of EndoMT in the context of tumor progression.

Dickkopf-1, the Wnt antagonist, is induced by acidic pH and mediates epithelial cellular senescence in human reflux esophagitis

Squamous esophageal epithelium adapts to acid reflux-mediated injury by proliferation and differentiation via signal transduction pathways. Induction of the Wnt antagonist Dickkopf-1 (Dkk1) is involved in tissue repair during inflammation and cellular injury. In this study, we aimed to identify the biological role of Dkk1 in human reflux esophagitis with respect to cell growth and regulation of Wnt signaling. Esophageal biopsies from reflux-esophagitis patients (n = 15) and healthy individuals (n = 10) were characterized in terms of Dkk1 expression. The role of Dkk1 in response to acid-mediated epithelial injury was analyzed by cellular assays in vitro utilizing squamous esophageal epithelial cell lines (EPC1-hTERT, EPC2-hTERT, and HEEC). Dkk1 was significantly overexpressed in human reflux-esophagitis tissue compared with healthy esophageal mucosa at transcriptional and translational levels. After acute and chronic acid (pH 4) exposure, esophageal squamous epithelial cell lines expressed and secreted high levels of Dkk1 in response to stress-associated DNA injury. High extracellular levels of human recombinant Dkk1 inhibited epithelial cell growth and induced cellular senescence in vitro, as demonstrated by reduced cell proliferation, G0/G1 cell cycle arrest, elevated senescence-associated β-galactosidase activity, and upregulation of p16. Acid pulsing induced Dkk1-mediated senescence, which was directly linked to the ability of Dkk1 to antagonize the canonical Wnt/β-catenin signaling. In healthy esophageal mucosa, Dkk1 expression was associated with low expression of transcriptionally active β-catenin, while in reflux-esophagitis tissue, Dkk1 overexpression correlated with increased senescence-associated β-galactosidase activity and p16 upregulation. The data indicate that, in human reflux esophagitis, Dkk1 functions as a secreted growth inhibitor by suppressing Wnt/β-catenin signaling and promoting cellular senescence. These findings suggest a significant role for Dkk1 and cellular senescence in esophageal tissue homeostasis during reflux esophagitis.

Wnt/β-Catenin Signaling Activation beyond Robust Nuclear β-Catenin Accumulation in Nondysplastic Barrett’s Esophagus: Regulation via Dickkopf-1

INTRODUCTION: Wnt/β-catenin signaling activation has been reported only during the late steps of Barrett’s esophagus (BE) neoplastic progression, but not in BE metaplasia, based on the absence of nuclear β-catenin. However, β-catenin transcriptional activity has been recorded in absence of robust nuclear accumulation. Thus, we aimed to investigate the Wnt/β-catenin signaling in nondysplastic BE. METHODS: Esophageal tissues from healthy and BE patients without dysplasia were analyzed for Wnt target gene expression by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and immunohistochemistry. Esophageal squamous (EPC1-& EPC2-hTERT), BE metaplastic (CP-A), and adenocarcinoma (OE33) cell lines were characterized for Wnt activation by qRT-PCR, Western blot, and luciferase assay. Wnt activity regulation was examined by using recombinant Wnt3a and Dickkopf-1 (Dkk1) as well as Dkk1 short interfering RNA. RESULTS: Wnt target genes (AXIN2, c-MYC, Cyclin D1, Dkk1) and Wnt3a were significantly upregulated in nondysplastic BE compared with squamous mucosa. Elevated levels of dephosphorylated β-catenin were detected in nondysplastic BE. Nuclear active β-catenin and TOPflash activity were increased in CP-A and OE33 cells compared with squamous cells. Wnt3a-mediated β-catenin signaling activation was abolished by Dkk1 in CP-A cells. TOPFlash activity was elevated following Dkk1 silencing in CP-A but not in OE33 cells. Dysplastic and esophageal adenocarcinoma tissues demonstrated further Dkk1 and AXIN2 overexpression. CONCLUSIONS: Despite the absence of robust nuclear accumulation, β-catenin is transcriptionally active in nondysplastic BE. Dkk1 overexpression regulates β-catenin signaling in BE metaplastic but not in adenocarcinoma cells, suggesting that early perturbation of Dkk1-mediated signaling suppression may contribute to BE malignant transformation.

Sa1804 Dysregulation of WNT5A/ROR2 Signaling Pathway Characterizes the Progression of Barrett's-Associated Esophageal Adenocarcinoma

BACKGROUND. Colorectal cancers (CRC) account for nearly 10% of cancer deaths in industrialized countries. Recent evidence points to a central role for the nuclear receptor Liver Receptor Homolog-1 (LRH-1) in intestinal tumorigenesis. Interaction of LRH-1 with the Wnt/β-catenin pathway, highly active in a critical subpopulation of CRC cancer cells, underscores the importance of elucidating LRH-1s role in this disease. Reduction of LRH1 diminishes tumor burden in murine models of CRC. The central role of receptor LRH-1 in CRC pathogenesis and a wealth of structural data at atomic resolution make LRH-1 an attractive target. Methods: To evaluate the contributions of LRH-1 to CRC growth, we constructed stably transduced CRC cell lines expressing Tet-inducible shRNA directed against LRH-1. Cell growth of the LRH-1 knockdown lines was compared with growth of cells expressing a non-silencing control RNA. To explore alterations in gene expression due to LRH-1 suppression, we performed a microarray analysis of our knockdown cell lines. Additionally, we sought to develop and characterize specific, non-cytotoxic inhibitors of LRH-1 function for use as both potential therapeutic agents and more broadly as research tools to study organogenesis and tumorigenesis. We applied differential scanning fluorimetry (DSF), used to measure qualitative binding, to screen over 200 compounds for association with the LRH-1 ligand binding domain. Results: LRH-1mRNA knockdown results in impaired cell proliferation. Cluster analysis of microarray gene expression demonstrates significant alterations in signal transduction, bile acid and cholesterol metabolism, and control of apoptosis. Moreover, we discovered 9 unique compounds that interact with LRH-1, but not the closely related receptor SF-1. We have further demonstrated that four of these compounds have antiproliferative effects with IC50 values ranging from 8.6 to 30 μM. Conclusions: Silencing of LRH-1 expression in CRC cell lines leads to impaired cell growth, demonstrating that LRH-1 is a viable target in CRC. LRH-1 may exert its effects via multiple signaling networks, with inhibition leading to cell cycle arrest or apoptosis. General features for binding shared between all compounds include a linear array of hydrophobic groups with polar atoms likely allowing for registration within the hormone pocket. Interestingly, two compounds showing antiproliferative activity share a cholesterol motif which may be related to LRH-1s function in bile acid and cholesterol homeostasis. Support: K12 HD07222, F32 CA163092, T32 DK007762